History and Objectives: Since arterial Oxygen saturation variations during diagnostic and therapeutic procedures, i.e. bronchoscopy and reported discrepancies on the prevalence of such condition and in order to determine the arterial Oxygen saturation (SPo2) during the passage of the bronchoscope through different part of the respiratory tract, the present investigation was undertaken on individuals referred to the out-patient clinic or hospitalized at the Imam Khomeini hospital of Tabriz (1994).

Materials and Methods: A descriptive study was conducted on 200 bronchoscopy candidates. Information pertaining to the personal data age, sex, major complaint, type of cardiac complication was recorded. At various stages of bronchoscopy (Before and after Oxygen administration, during Xylocaine treatment of the vocal cords, passage of the bronchoscope from the main body of the right and left bronchus, during washing and biopsy of the bronchus, during coughing and at the end of coughing), reduction of Oxygen saturation (More than 5%) was taken as the fall of the arterial Oxygen saturation.

Results: From 200 cases studied, 79 patients (39.5%) displayed fall of SPo2. 31 patients (15.5%) showed a fall of more than 10%. Total of 165 SPo2 falls were recorded during various stages of bronchoscopy. Falls were especially significant during later stages of bronchoscopy and during the washing stage, the passage of the bronchoscope through the main body of right principle bronchus and during biopsy. Correlation between atelectasis and fall of SPo2 was 0.24 and between cigarette smoking and fall of SPo2 was 17% and between occurrence of arrhythmia and fall of SPo2 was 0.25.

Conclusion: Since the fall of SPo2 is quite frequent during bronchoscopy, administration of the Oxygen before bronchoscopy and monitoring of the arterial Oxygen saturation by pulse oximeter during bronchoscopy is highly recommended. Further analytical investigation to the role of atelectasis and cigarette smoking on the fall of SPo2 is recommended and more experimental analysis in this subject is recommended.